Texture/material problem

Everything has worked well with my project until I recently tried to use some self-made textures. When loading the track the game shows an error: "Error loadng texture x for material y". The material name has been set as wall in BTB. When I tick the checkbox Keep material name it now loads the track but shows some kind of placeholder in place of the textures. I have also tried to change the texture names in the rFactor folder, but that doesn't work either.

This has been probably asked hundreds of times, but I'm really out of ideas with this.

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Texture sizes are correct and they are all dds-files. But now while checking the sizes I noticed that the material names are probably wrong, as they don't have the word wall in front of them. Maybe I'll fix the names tomorrow and try it again.

Now I have changed the material and texture names in the xPack, so they now have the wall_ in their names and changed all the materials in BTB to the renamed ones, but the game still somehow fails to load the textures. Keep material name is also unticked.

It really seems like those textures just don't want to show. I just remade and reinstalled the whole xPack and changed the materials to the new ones in BTB again, but the track still keeps crashing.

Interestingly, now the first material to cause the crash isn't called wall79 as before, but now it's the wall188. I wonder if the names for walls etc in the rfactor folder aren't the same as they are in BTB, because neither of those walls should have the texture the game is trying to load for them.